firebase emulator not working

I attempted to follow this step [here](https://firebase.google.com/codelabs/firestore-web#4) but when I ran the command `firebase emulators:start --only hosting` it would gave me the following error `Error: Could not start Hosting Emulator, port taken.`

```
firebase emulators:start --only hosting
i emulators: Starting emulators: hosting
i emulators: Shutting down emulators.
i hub: Stopping emulator hub
⚠ hosting: Port 5000 is not open on localhost, could not start Hosting Emulator.
⚠ hosting: To select a different host/port, specify that host/port in a firebase.json config file:
{
// ...
"emulators": {
"hosting": {
"host": "HOST",
"port": "PORT"
}
}
}
i emulators: Shutting down emulators.

Error: Could not start Hosting Emulator, port taken.
```

I think a fix is to add the following in `firebase.json` file, though wonder if there's a way to use dynamic open port variables instead of hardcoding ones:

```
"emulators": {
"firestore": {
"port": 5002
},
"functions": {
"port": 5001
},
"hosting": {
"port": 5005
}
},
```

Start by inspecting the repository's firebase.json and reproducing `firebase emulators:start --only hosting` to confirm the port conflict. Compare the existing emulator configuration with the proposed Firestore, Functions, and Hosting ports; done means the documented setup starts successfully without the reported error.

Written by the indexing model from the issue text.